The invention relates to a photomultiplier tube segmented into a plurality of elementary photomultipliers.
One of the technical problems to be solved in the photomultiplier tubes segmented into a plurality of elementary photomultipliers is related to the field of high-energy physics and particularly to the photo-electric detection of elementary particles in order to determine, for example their trajectory. For this purpose it is necessary to realize detection devices comprising a large number of distinct photomultiplier elements which are placed as close as possible together so as to limit the losses of the useful area of these devices. A solution to this technical problem, which has also the advantage of reducing the cost of the above-mentioned detection devices, is generally given by the segmentation of a photomultiplier tube into a plurality of elementary photomultiplier. The fact that several photomultipliers are thus realized in one and the same enclosure contributes to a maximum utilization, without any losses, of the photocathode surface of the photomultiplier tube. The cost price of the photomultiplication channels thus obtained is considerably less than that of an equivalent number of single photomultiplier tubes.
French Patent Application No. 83,11,514 which corresponds to U.S. Pat. No. 4,649,314 describes a particular embodiment of a photomultiplier tube segmented into a plurality of elementary photo multipliers and comprising a photocathode and a multiplier of the type using sheets partitioned in a plurality of elementary multipliers associated with the said elementary photomultipliers. This known segmented photomultiplier tube functions by means of proximity focussing, that is to say that the laminated multiplier is placed in the vicinity of the photocathode. Each elementary multiplier thus cuts up, in an immaterial way, the surface of the photocathode into elementary photocathodes which are perfectly contiguous and without any losses. Although it has the advantage of providing up to 64 measuring channels in one and the same enclosure, this known tube type has the drawback that due to the presence of metallic assembly fittings and electrical contacts at the periphery of the laminated multiplier the useful area of the photocathode is smaller than the overall space of the tube and consequently it is impossible to give such tubes, for example a mosaic structure without creating important zones at the area of their junctions which are insensitive to radiation to be detected. On the other hand the cost of these tubes is still relatively high due to the fact that they require a cumbersome manufacturing technique because the photocathode must be vapour-deposited in vacuum on the exterior of the tube whereafter it is mounted on this tube, which is due to the proximity of the multiplier and the photocathode.